Botanists have long studied the effects of various stimuli on plant growth. The phenomena of phototropism, geotropism and chemotropism by which external stimuli of light, gravity and chemicals bring about directionally oriented plant growth are well characterized. It is known that phytohormones mediate cellular differentiation and that a specific complement of nutrients must be available to support plant growth. Advances in the understanding of plant physiology have contributed greatly to the development of agricultural techniques which optimize crop production as well as facilitate the efficient operation of plant nurseries.
The control of plant growth and development through the application of plant hormones is widely used to promote root growth in the asexual reproduction of plants. This procedure is instrumental in establishing fruit orchards where unique plant varieties are propagated by means of cuttings and through the grafting of scions on root stalks. In essence, an auxin such as indoleacetic acid is applied to the cut end of a plant to stimulate root formation. Plant hormones are also utilized to retard the formation of abscission layers in an effort to prevent early drop of fruit. It will be appreciated by those skilled in the art that early drop causes an unripened fruit crop. Synthetic auxins such as alpha naphthalene acetic acid have been applied successfully to control fruit set and also to regulate flowering time.
More recently, the use of tissue cultures to regenerate plants from cell suspensions or protoplasts, particularly for the propagation of virus-free plants, has received wide spread attention. In experiments by Shillito and others and by Prioli and others, plant regeneration of maize protoplasts was investigated as a possible solution to the problem of time-intensive back-crossing.
In plant tissue and organ culture, a plant organ or cell aggregate is removed from a plant and placed in a nutrient solution. The plant cells continue to grow and divide, forming a callus which then forms shoots and roots. The plantlets or embryoids are placed in media which promotes leaf expansion and internode elongation. The plantlets can then be grown to maturity in soil. This technique is particularly desirable as an adjunct to gene transfer and somatic hybridization procedures.
These efforts, in addition to selective breeding and fertilizer use, underscore the long felt need to increase the rate at which plant growth occurs. As will be described hereinafter, the present invention provides a method and apparatus by which plant growth can be regulated.
In recent years, multi-disciplinary investigations have provided evidence suggesting that electric and magnetic fields play an important role in cell and tissue behavior. In U.S. Pat. No. 4,818,697, entitled "Techniques For Enhancing The Permeability Of Ions Through Membranes," and its continuation application, Ser. No. 280,848, filed on Dec. 7, 1988, which have been assigned to the assignee of the present invention and the disclosures of which are incorporated herein by reference, a method and apparatus are disclosed by which transmembrane movement of a preselected ion is magnetically regulated using a time-varying magnetic field. The fluctuating magnetic field is preferably tuned to the cyclotron resonance energy absorption frequency of the preselected ion. This important discovery brought to light the interplay of local magnetic fields and frequency dependence in ion transport mechanisms. It has now been discovered that by utilizing and extending the principles of cyclotron resonance tuning, unexpected and remarkable advances in the control and modification of growth processes of plants can be achieved.
The U.S. Patent Application Ser. No. 236,044, filed on Aug. 24, 1988, entitled, "Method And Apparatus For Controlling The Rate Of Eukaryotic Fermentation," which has been assigned to the assignee of the present invention and the disclosure of which is incorporated herein by reference, the discovery that cyclotron resonance regulation can be utilized to control the rate of fermentation of a substrate by eukaryotes is disclosed. In a number of copending patent applications which are assigned to the assignee of the present invention, more specifically, U.S. Patent Application Ser. Nos. 172,268 (filed Mar. 23, 1988); 254,438 (filed Oct. 6, 1988); 295,164 (filed Jan. 9, 1989); the disclosures of which are incorporated herein by reference, it is disclosed that cyclotron resonance regulation is effective in controlling the development of living human tissue.
In U.S. Patent Application Ser. No. 109,783, filed Oct. 16, 1987, entitled "A System for Controlling Cell Behavior Using an Applied Oscillating Magnetic Field," which is assigned to the assignee of the present invention and the disclosure of which is incorporated herein by reference, the present inventors disclose the use of cyclotron resonance for controlling cell motility.
In U.S. Patent Application Ser. No. 343,017, filed Apr. 25, 1989 entitled "Methods And Apparatus For Regulating Transmembrane Ion Movement Utilizing Selective Harmonic Frequencies And Simultaneous Multiple Ion Regulation," the disclosure of which is incorporated herein by reference, the present inventors disclose a method of utilizing higher-harmonic frequencies for ion transport and a method of simultaneously controlling multiple ions.
It is an object of the present invention to provide a method and apparatus by which the rate of plant growth can be increased, or alternatively decreased.
It is a further object of the present invention to provide such a method and apparatus for controlling plant growth rates which allows for the selective control of differential growth processes such as flower and fruit maturation.